Ootsuka Y, Xu T, Terui N
Institute of Basic Medical Sciences, University of Tsukuba, Ibaraki-ken, Japan.
J Auton Nerv Syst. 1995 Aug 4;54(2):89-103. doi: 10.1016/0165-1838(94)00194-o.
To examine the origin of the so-called '10-Hz rhythm' in the sympathetic nerves, the mass discharges of the white ramus of the third thoracic segment (T3WR) and the inferior cardiac nerve (ICN) and the activities of single postganglionic neurons in the stellate ganglion were recorded in spinal cats. During the chemical or electrical stimulation of the spinal cord, the time of peak of discharges in the sympathetic nerves was analyzed. Both intrathecal administration of N-methyl-D-aspartic acid (NMDA; 3-10 mM) and continuous high frequency (80-200 Hz) electrical stimulation of the dorsolateral funiculus at the second cervical level increased activity of the sympathetic nerves in a similar fashion. In these conditions, modes of the inter-peak interval histograms (IPIH) were about 100 ms (range; 90-130 ms), the inverse of about 10 Hz, but no correlation was observed in autocorrelograms of these peaks of discharges. Therefore, this 100-ms interval activity might have some significance for the 10-Hz rhythm. In order to make this point clear, we stimulated the dorsolateral funiculus with intermittent trains of electrical pulses (0.2-ms duration, 10-35 pulses of 80-200 Hz frequency, in every 300-800 ms). While intermittent trains of pulses were applied, multiple peaks of discharges were evoked in the sympathetic nerves. IPIHs of the nerves were multimodal. The first mode (shortest interval) was about 100 ms. The first mode depended on none of the stimulus parameters but the probability of the about 100-ms interval activity depended on the interval of trains of pulses and the stimulus intensity. With this intermittent stimulation, the autocorrelogram of the peaks revealed the 100-ms interval rhythm. To confirm that the peak of discharges in the ICN was composed of synchronized spikes of postganglionic fibers, single neuronal activities of postganglionic neurons were recorded during the intermittent stimulation. Inter-spike interval histograms showed almost same profile as the IPIHs of the ICN. These results can be explained if the following two assumptions are valid; (i) There are mechanisms that limit minimum firing interval of most preganglionic neurons to about 100 ms. (ii) Simultaneously a interneuron in the spinal cord resets the spike generation of multiple preganglionic neurons. Similarity of the spike activities of the sympatho-excitatory reticulospinal neurons to the intermittent stimulation can explain the 10-Hz rhythm in the peripheral sympathetic nerves in intact spinal cord animals. It is not necessary to postulate the specific 10-Hz rhythm generator in the brain stem for the sympathetic nervous system.
为研究交感神经中所谓“10赫兹节律”的起源，在脊髓猫中记录了第三胸段白交通支（T3WR）和心下神经（ICN）的群体放电以及星状神经节中单个节后神经元的活动。在对脊髓进行化学或电刺激期间，分析了交感神经放电峰值出现的时间。鞘内注射N-甲基-D-天冬氨酸（NMDA；3 - 10 mM）以及在第二颈椎水平对背外侧索进行持续高频（80 - 200 Hz）电刺激，均以类似方式增加了交感神经的活动。在这些条件下，峰间期直方图（IPIH）的模式约为100毫秒（范围为90 - 130毫秒），即约10赫兹的倒数，但在这些放电峰值的自相关图中未观察到相关性。因此，这种100毫秒间隔的活动可能对10赫兹节律具有某种意义。为明确这一点，我们用间歇性电脉冲串（持续时间0.2毫秒，频率80 - 200 Hz，每300 - 800毫秒10 - 35个脉冲）刺激背外侧索。当施加间歇性脉冲串时，交感神经中诱发了多个放电峰值。神经的IPIH是多峰的。第一种模式（最短间隔）约为100毫秒。第一种模式不依赖于任何刺激参数，但约100毫秒间隔活动的概率依赖于脉冲串的间隔和刺激强度。通过这种间歇性刺激，放电峰值的自相关图显示出100毫秒的间隔节律。为证实ICN中的放电峰值由节后纤维的同步尖峰组成，在间歇性刺激期间记录了节后神经元的单个神经元活动。峰间期直方图显示出与ICN的IPIH几乎相同的特征。如果以下两个假设成立，这些结果可以得到解释：（i）存在将大多数节前神经元的最小放电间隔限制在约100毫秒的机制。（ii）同时脊髓中的一个中间神经元重置多个节前神经元的尖峰产生。交感神经兴奋性网状脊髓神经元的尖峰活动与间歇性刺激的相似性可以解释完整脊髓动物外周交感神经中的10赫兹节律。对于交感神经系统，无需假定脑干中有特定的10赫兹节律发生器。
